The Flux Distributions of Be Stars in the Far-UV

Abstract

AbstractThe initial results of a program to investigate the far-UV (500-1700 A) spectra of Be stars using the Voyager ultraviolet spectrometers axe presented. Observations of eleven Be stars, with spectral types from B0 through B7, obtained between March 1979 and July 1984 are discussed. The Voyager resolution (∼15 A) allows only limited spectroscopic studies; shortward of 1150 A C III λ977 and LyJβ λ1025 are the most prominent spectral features. Two stars, γ Cas and 59 Cyg, showed enhanced C III λ977 absorption. The flux distributions of the Be stars were intercompared with those of reference stars with low projected rotational velocities and, in a parallel study, to predictions from rotating star models. The model calculations suggest that the observable effects of a high rotational velocity (V≳ 0.9 of critical velocity) on the flux distribution are small except in the FUV (λ < 1150A). The Voyager flux distributions were found to be indistinguishable from those of the low v sin i reference stars. No evidence was found for critical rotation in Be stars. All observations were consistent with Be stars rotating at less than 0.85 of critical velocity.